Flexible fixed set portioning and performance improvement in OVSF based networks

摘要

The limited codes in orthogonal variable spreading factor (OVSF) based CDMA networks need efficient code assignment. With the continuous progress in code assignment research, the efficiency reaches close to 100 percent. However, the cost and complexity in these schemes increases significantly. For real time calls there is an additional requirement of minimizing call establishment delay which is directly proportional to the number of code searches before assignment. Therefore to design a good code assignment scheme the system has to sacrifice some performance measure. Fixed set partitioning (FSP) is known to be the best method for real time calls handling. This paper describes a flexible fixed set partitioning (FFSP) scheme which is the extension of FSP scheme. The scheme is suited for real time applications as the code searches (which reduces to call establishment delay) in the proposed scheme are fewer than most of the proposed schemes. The code searches are higher in FFSP schemes as compared to FSP scheme, and also the code blocking probability is significantly reduced due to flexibility of controlled region overlapping. The simulation results verify the reduction in number of code searches.